Usually, the causes of anal fissure are: dry stool, diarrhea and spasm of internal sphincter. 1. Dry stools: too dry or too hard stools will lead to straining during defecation, which will hurt the anal canal, thus hurting the perianal skin, tearing and causing anal fissure. 2. Diarrhea: because the stool is too thin, often contains some bacteria into the anal crypt, the anal crypt secondary infection, perianal tissue inflammation, edema will also form anal fissure. 3. Internal sphincter spasm: anal tissue inflammation, the patient’s mental state of tension or anal pain caused by anal spasm, this situation is also easy to cause anal fissure. It should be noted that when the patient has anal fissure phenomenon, should consult the doctor in a timely manner, clear specific reasons, under the guidance of the doctor to deal with as soon as possible.